The present invention relates to a process and an apparatus for the manufacture of a metal foil wherein the metal foil is deposited electrolytically on an endless carrier belt, preferably on an endless metal belt.
In known processes for the manufacture of metal foils such foils, in particular copper foils, are deposited electrolytically on drums. These drums are connected as cathode and dip by about 40% of their circumference into an aqueous metal salt solution. The anodes are arranged at a distance of about 10 mm from the drum periphery. The metal is deposited on the drum by electric current. The rate of rotation of the drum and the current setting dictate the desired foil thickness, about 20,000 to 25,000 ampere per drum being conventionally used.
The metal foil so produced is drawn off the drum, wound up and subsequently subjected to further treatment in a separate plant.
In such subsequent treatment the individual metal foils are connected to form an endless belt, are conveyed through a plurality of galvanic cells and the desired metal or alloy coatings are applied.
The above process has by now received world-wide acceptance although it suffers from numerous drawbacks. For example the foil texture cannot be influenced by different current densities because only a given current density can be applied to a given drum. Moreover the subsequent treatment must be conducted in a separate plant, necessitating cumbersome and time-consuming operations. Finally, an important drawback of the above described process resides in the fact that in particular thin metal foils having thicknesses below 10 .mu.m cannot be produced, because such foils cannot be wound.
A process has become known from U.S. Pat. No. 4,108,737 (Ehrhardt et al.) for the manufacture of super-conductive foils, strips or wires by electrolytic deposition on an endless steel belt. However, the deposition in principle proceeds in the same manner as was described above. The carrier belt is accommodated in the one and only deposition cell being wound about a single drum which dips into the liquid as is apparent particularly from the drawing of that U.S. Pat. No. 4,108,737.
Only one particular strength of current can be applied to this drum, and the carrier belt merely serves the purpose of facilitating the passage of the foil through passivating and cleaning baths by means of the carrier belt. Such cleaning treatment would be possible on the drum itself at great expenditure only. This process as well is subject, in respect of the deposition, to the same drawbacks as the previously recited method.